干扰素诱导基因ASB13拮抗流感病毒复制机制研究

Innate immune response provides a robust first line of defense against influenza A virus infection. A major component of the induced innate immune response to viral infections is the activation of antiviral interferons (IFNs), which transcriptionally induce hundreds of interferon-stimulated genes (ISGs). The ISG response facilitates clearance of virus from infected cells, establishes a protective antiviral state in uninfected cells, and promotes adaptive immune responses. Although several ISGs have been shown to play critical roles in host defense against influenza infections, the antiviral functions and the mechanisms of actions for most ISGs against influenza A virus have not yet been established. Our preliminary studies have shown that an IFN-α inducible ISG ASB13 can effectively inhibit the replication of influenza A virus in 293T and A549 cells, and our unbiased antiviral screening for the interactions between host ISGs and individual influenza viral proteins has revealed that ASB13 protein interacts with nonstructural protein NS2/NEP. As ASB13 is the component of a multimeric E3 ubiquitin ligase, which can mediate the degradation of the target protein. So we hypothesize that ASB13 inhibit the replication of influenza virus through mediating the degradation of the NS2/NEP protein. In this proposal, we will further test this hypothesis, and reveal the molecular mechanisms that responsible for the antiviral activity of ASB13 against influenza A virus.

干扰素刺激基因(interferon-stimulated gene, ISG)在机体抗病毒天然免疫应答过程中发挥着重要作用，但是大多数ISG的相关功能及其机制还不清楚。我们的前期研究表明，ASB13这一由IFNα特异性诱导表达的ISG，能够在A549细胞和293T细胞上有效抑制流感病毒的复制；另外，我们还发现流感病毒非结构蛋白NS2/NEP与ASB13蛋白有较强的特异性相互作用。鉴于ASB13能够与Elongin B/C、Cullin 5和Rbx2蛋白形成一个多亚基E3泛素连接酶，能够介导与其结合靶蛋白的泛素化降解。所以，我们提出假设认为ASB13是通过介导NS2/NEP发生泛素化降解，而起到抑制流感病毒复制的作用。本研究拟对该假设进行全面的验证，从而阐明ASB13拮抗流感病毒复制的分子机制。

干扰素介导的天然免疫应答是机体抵御病毒侵染的第一道防线，其主要机制是诱导数百个干扰素刺激基因(interferon-stimulated gene, ISG)的表达。这些ISG的编码蛋白，一方面会直接起到抗病毒的作用；另一方面也能够调节机体各种免疫反应，而使机体建立抗病毒状态。虽然一些ISG已经被证明在机体抵御流感病毒感染的过程中发挥着重要作用，但是大多数ISG的相关功能及其机制还不清楚。我们的研究表明，ASB13这一由IFNα特异性诱导表达的ISG，能够在A549细胞和293T细胞上有效抑制流感病毒的复制；对相关机制的研究发现，ASB13蛋白与流感病毒非结构蛋白NS2/NEP能够发生较强的特异性相互作用，并通过形成NS2/NEP-ASB13-Elongin B/C-Cullin 5-Rbx2-E3泛素连接酶复合体介导NS2/NEP发生K63泛素化，影响NS2/NEP对病毒核糖核酸核蛋白的核输出功能，从而起到抑制流感病毒复制的作用。本研究的完成为我们进一步认识IFN拮抗流感病毒复制的分子机制提供线索